female infanticide

Rob Quinlan (C611417@MIZZOU1.MISSOURI.EDU)
Mon, 5 Dec 1994 12:58:58 CST

Mike Lieber suggests that Yanomamo female infanticide is a mechanism (or
something) for population regulation. Evolutionary biologists and anthropologi
sts have been working on infanticide and biases in parental care for a little
while and nearly none suggest population regulation as the explanation. (Such
explanations are usually attributable to the off hand comments of ethnographers
encountering this phenomenon while studying something else.) In polygynous
cultures (or species) the variance in reproductive success(RS) is greater among
males than it is among females. The logic is obvious, but I'll point it out
anyway. Female RS is ultimately constrained by the number of pregnancies she
can have, while male RS is constrained by the number of copulations he can get.
In polygynous societies some males go without while others do quite well (femal
es all do about the same in terms of RS).

Given that an INDIVIDUAL only has so much to give her/his/per offspring they
sometimes must make painful decisions about how to allocate those resources
among their present and future children. (This is where the concept of parenta
l investment comes from.) To an extent male RS depends on the investment
he got from his parents. The addition of a baby sister can mean a significant
reduction in the RS of her brother. At this point its a matter of simple math
(at least in an evolutionary perspective). Lets suppose that the RS of the
male raised by himself = 15, and that the RS of any female = 5, and the RS of
the male raised with his sister = 5. Thus the inclusive fitness of a parent
with a male and female offspring = 10, while the inclusive fitness of a parent
with a male only = 15. Such mathematical reality leads to cost benefit analysi
s that sometimes suggests infanticide as the best alternative. Although, there
are, ofcourse, many other factors in the equation -- not least of which is the
resource base of the parents making the decision.

There is ample literature on this topic (if anyone really cares I could suggest
some). Not least of which is a test of this hypothesis (usually called the
Trivers-Willard hypothesis after the guys who thunk it) for the Yanomamo. If
I remember correctly for the Yanomamo the variables used were male status and
sex ratio of the family. They used male status as a measure of the parental
ability to raise competitive males. The authors found that there was no
relationship between the variables. However, the finding is problematic, becau
se there is a helluva lot more to parental investment (PI) than male status.
For example, they could've looked at female status. Did first wives have
higher sex ratios? There were probably other problems too. Anyway, at least
one of the authors is on this list and it might be nice to hear him comment.

Another case comes to mind from Lee Cronk's work w/ the Mukugodo (sp?). They
are an ex-foraging group living near cattle herding neighbors. I think the
short version of the story goes like this: They tend to marry out of the group,
they have low status relative to their neighbors, thus it's hard for Mukugodo
man to get a wife (males have low RS), thus the sex ratio favors females --
partially as the result of MALE infanticide.

So, I guess my question is this. If we as anthros are going to get involved in
interventions w/ other (less knowledgeble peoples?) on whose information are we
going to base these interventions? And hadn't we better work a lot harder at
getting it right rather than going on endlessly about epistemology? After all,
I think most of us would rather go to a doctor that knew her/his/per anatomy
well than to one who understood the philosophical underpinnings of such

Rob Quinlan
Graduate Student, Dept. of Anth., U. of Missouri-Columbia

P.S. Does anyone remember "Golden Marshal Town"?